I'll send a PM to the author of this texture pack so he/she can maybe make a sidenote of this fix. If you have an ATI Video card, are trying to use the 256x Texture Pack and are getting crashes, you need to do the following. (If you are on Windows 7 64-Bit)
3. Un-patch your minecraft.jar with MCPatcher (the new one), then click Options and change the heap size to 768. After that, patch Minecraft with MCPatcher.
4. Run Minecraft, open the Texture Packs folder and copy in PhotoRealism.x256.zip. Click it inside the MC Client, once, and wait. Once the client has changed textures, you can be sure the Texture Pack is working.
5. Enjoy. Hope this works. If it doesn't I can't help you, this is just what I did.